The invention relates to an imgage-processing device for estimating the displacement D(i) of objects situated in said image, comprising an estimation arrangement providing for each picture element i, a displacement vector DK(Zi) from two successive images I(Z.sub.i, t) and I(Z.sub.i, t-TR) separated by a period TR.
The quantities I(Z.sub.i, T+) and I(Z.sub.i, t-TR) represent the luminance of picture element i, whose coordinates will be indicated by Z.sub.i. If necessary, reference will be made to the vertical coordinate indicated by y.sub.i and the horizontal coordinate indicated by x.sub.i.
This device is particularly useful in the field of digital television transmission systems in which it is attempted to transmit sequences of images at bit rates which are as small as possible, while maintaining a satisfactory quality. For example, for obtaining a rate which is twice as small, it has been recommended where only every other image of a sequence is transmitted, which case necessitates a reconstruction of the missing images by means of interpolation if the sequence at the receiver end is to be regenerated. In such cases the displacement values D(i) characterizing the movement from one image to the other image are used to derive the interpolation images IP at the instant t-TR/2 in accordance with the formula: EQU IP[Z.sub.i +, t-(TR/2)]=1/2{I[Z.sub.i -D(Zi)/2, t-, TR]+I[Z.sub.i +D(Zi)/2, t]}
A device according to the invention can also be used for tracking targets, in cell biology analysis, etc.
The Article entitled "Kalman Filter Formulation of Low Level Television Image Motion Estimation" by John STULLER and Goplan KRISHNAMURTHY in the magazine Computer Vision Graphics and Image Processing, No. 21, 1983, pages 169 to 204 describes the use of the Kalman filtering concept for estimating the motion of objects in a television image.
It is known that this concept is effective in this technique, though experiments have shown that there is a risk of poor estimation and even of divergence of the filter.